This invention relates to techniques for characterizing and fingerprinting digital video object. In particular, this invention relates to method and system for generating a unique and robust identifier for a digital video object based on multiresolution, multirate spatial and temporal signatures.
Digital video has become very popular in the last decade. There are many sources from which digital video is created, recorded and distributed, such as DV camcorders, DVD, DVR, and video download and streaming over the Internet. A piece of digital video is called a digital video object or simply video object in this document. It may be a file that is saved on a storage media such as a hard disk drive, or a bitstream that is transmitted over a broadcast channel or over the Internet. The constantly increasing number of digital video objects and proliferation of digital video entertainment and services demand effective and efficient methods and systems for indexing and identifying digital video objects.
A common method for uniquely identifying a digital object is to pass it through a hash function that produces a fixed-length output known as hash sum or message digest. A popular hash function is MD5 that is specified by RFC 1321. While a hash sum as an identifier is useful for certain purposes such as data integrity check, it is often inadequate for content identifications. For example, a digital video object may be encoded in various formats such as MPEG4 and Windows Media, and at various bitrates such as 2 Mbps for broadcast and 700 Kbps for Internet download. The hash sum value will be different for each of these formats though the content is the same. A fingerprint of a digital video object is different from a hash sum in that the former is a unique identifier for the video content while the latter is a unique identifier for the file. Having a unique and robust fingerprint for each and every video object enables many applications, such as video content indexing, search and retrieval, content filtering, broadcast monitoring, and metadata services.